Faculdade de Engenharia da Universidade do Porto
The Use of Thermal Infra-red Imaging to Reveal
Muscle Injuries Caused by Physically Demanding
Jobs in Industrial Operations
Selma Renata Almeida Pinho
Dissertação realizada no âmbito do
Mestrado de Engenharia Biomédica
Orientador: Prof. Doutor Paulo José Cerqueira Gomes da Costa
v
Resumo
As Lesões Musculosqueléticas (LME) podem afetar diversas partes do corpo e quando surgem através da atividade profissional são designadas por Lesões musculosqueléticas relacionadas com o trabalho (LMERT). Pretende-se avaliar a possibilidade de usar a termografia como uma ferramenta de diagnóstico preliminar na deteção e monitorização de trauma e ocorrência de lesões.
O aparelho utilizado foi uma camara térmica, em que consegue detetar o calor produzido pelo corpo humano. A partir desta camara adquiriu-se várias imagens térmicas. As imagens foram processadas em software Matlab, com recurso a operações de binarização e de morfologia. Todas as implementações foram realizadas em MATLAB com 26 casos reais de imagens térmicas com lesões musculosqueléticas variáveis e 26 casos reais de imagens térmicas sem qualquer tipo de lesão.
Foi realizada uma análise entre os diagnósticos obtidos pelo enfermeiro, pelo programa desenvolvido em Matlab, e pelo enfermeiro observando as imagens térmicas não processadas. Verificou-se concordância dos diagnósticos entre o programa desenvolvido em Matlab e o diagnóstico do enfermeiro olhando para as imagens térmicas não processadas.
Os resultados obtidos são gratificantes e demonstram o potencial da termografia como ferramenta de apoio ao diagnóstico do enfermeiro.
Palavras-chave: Termografia infravermelha, lesões musculosqueléticas relacionadas com o
vii
Abstract
The musculoskeletal injuries (MSIs) can affect various parts of the body and when they arise through professional activity are called work-related musculoskeletal disorders (WMSDs). It is intended to assess the possibility of using thermography as a primary diagnostic tool in detecting and monitoring the occurrence of trauma and lesions.
The device used was a thermal camera, which can detect the heat produced by the human body. From this chamber was acquired several thermal images. The images were processed using Matlab software, using binarization and morphological operations. All implementations were done in MATLAB with 26 actual cases of thermal images with musculoskeletal injuries variables and 26 real cases of thermal images without any injury.
An analysis of the diagnoses obtained by the nurse was done, the program developed in Matlab, and the nurse watching the unprocessed thermal images. There was agreement between the diagnostic program developed in Matlab and the nurse's diagnosis looking for unprocessed thermal images.
The results are gratifying and demonstrate the potential of thermography as a support tool for the diagnosis of nurses.
Keywords: Infrared thermography, work-related musculoskeletal disorders, industrial
vii
Index
1.
Introduction ... 1
1.1 - Problem Description ... 1 1.2 - Framework ... 1 1.3 - Goals ... 3 1.4 - Work Organization ... 32.
State of the Art ... 5
2.1 - Ergonomics ... 5
2.2 - Musculoskeletal Injuries ... 7
2.2.1– Work-Related Musculoskeletal Disorders ... 8
2.2.2– Incidence of work-related musculoskeletal disorders at a world level ... 9
2.2.3– Main Types of Work-Related Musculoskeletal Disorders ... 10
2.2.4– Risk Factors ... 13
2.3 - Thermography ... 15
2.4 - Types of Thermography ... 18
2.4.1– Liquid Crystal Thermography ... 18
2.4.2– Microwave Thermography ... 18
2.4.3- Infrared Thermography ... 20
2.5 - Thermography and Work-Related Musculoskeletal Disorders ... 28
2.5.1– Thermography as a Diagnostic Tool ... 28
2.5.2– Thermography as an Evaluation Tool of Exposure to Risk Factors for Development of Work‐Related Musculoskeletal Disorders... 29
2.6 - Conclusions ... 36
3.
Processing and Image Analysis ... 37
3.1 - Morphological Operations ... 37
3.1.1– Function bwmorph ... 38
3.1.2– Edge Detection using Function Edge ... 40
3.1.3– Function Regionprops ... 45
3.2 - Conclusions ... 47
4.
Methodological Procedures ... 49
4.1 - Operational Definition of Variables ... 49
4.2 - Materials and Methods ... 49
4.2.1– Population and Sample ... 50
viii
4.2.3– Environmental Preparation Protocol and Patient ... 51
4.2.4– Materials Used ... 51
4.2.5– Acquisition and Processing of Thermal Images ... 54
4.2.6– Software Features ... 55
5.
Results ... 57
5.1 - Patient Diagnosis ... 57 5.2 - Human Intervention ... 64 5.2.1– Images Unprocessed ... 64 5.3 - Automatic Processing ... 74 5.3.1– Experimental Group ... 75 5.3.2– Control Group ... 82 5.4 - Statistical Analysis ... 84 5.5 - Conclusions ... 85 5.6 - Discussion of Results ... 856.
Conclusions ... 88
6.1 - Proposal for Future Research ... 89
x
List of Figures
Figure 2.1 - Factors contributing to the success of an ergonomics program [19]. ... 6
Figure 2.2 - Proportion of occupational diseases in Europe workers in 2005 [31]. ... 9
Figure 2.3 - Percentage share of workers reporting health problems [31]. ... 10
Figure 2.4 - Pressured at carpal ligament [35]. ... 12
Figure 2.5 – Muscle Injury [46]. ... 13
Figure 2.6 - Risk factors for MSIs [31]. ... 14
Figure 2.7 - Body temperature in: a) a cold environment; b) in the warm [55]. ... 16
Figure 2.8 - IR image of healthy knee: a) anterior aspect; b) posterior aspect [61]. ... 17
Figure 2.9 - Prototype clinical MWT equipment [69]. ... 19
Figure 2.10 - Medical imaging techniques within the electromagnetic spectrum [61]. ... 20
Figure 2.11 - The thermal detector in an IR camera converts photon energy from a target surface into a thermal image that can be displayed on a computer monitor. Each colour hue on the thermal image corresponds to a certain temperature interval [70]. ... 21
Figure 2.12 - Temperature scales of thermograms: a) colour scale; b) colour scale strong-contrast; c) grey tones [71]. ... 22
Figure 2.13 - Thermal Transfer Processes [74]. ... 22
Figure 2.14 - IRT images showing examples of varicose and superficial veins [76]. ... 23
Figure 2.15 - Comparison of the pre-training and 24h post-training thermal image. (1) Subject of the control group, pre-training; (2) subject of the control group, 24h post-training; (3) subject of the experimental group, pre-training; and (4) subject of the experience. ... 24
Figure 2.16 - Representation of the classification of IRT-related factors in humans [76]. .... 25
Figure 2.17 - IR and adjacent spectral regions and expanded view of the so-called thermal IR. This is the region where IR imaging systems for shortwave (SW), midwave (MW), or long-wave (LW) cameras exist. Special systems have extended MW or SW ranges [82]. ... 26
Figure 2.18 – Planck Curve [86]. ... 27
Figure 2.19 – Procedure for the production of a thermal image: a) Object; b) IR Camera Flir; c) Thermal image [90,91]. ... 28
Figure 2.20 - Tsk measurements by IRT during running exercise [106]. ... 32
Figure 2.21 - IRT of right and left knees: a) before; b) after race for the participant with right knee OA [75]. ... 33
Figure 2.22 - Medial aspect of the left leg in the control (above) and experimental (below) groups, before (left) and after (right) whole body vibration [107]. ... 34
Figure 2.23 - The image is represented 2 and 3 a guy after fiddling with the shoulder at rest and images 4 and 5 without shoulder be at rest [108]. ... 35
Figure 2.24 - The effects of stress on hand thermogram (A) 10 min full recovery from the normal 1 min immersion in water at 20 ◦C; (B) in a patient with Raynaud's phenomenon after 10 min. (C); (D) Examples of hand arm vibration injury to certain fingers, showing d ... 35
xi
Figure 3.1 - Noisy fingerprint image. Opening followed by closing [112]. ... 39
Figure 3.2 – Fingerprint image from Fig. 9.11 thinned once. (b) Image thinned twice. (c) Image thinned until stability [112]. ... 39
Figure 4.1 – Camera Sony [117]. ... 52
Figure 4.2 – Hygrometer and tape measure [118]. ... 52
Figure 4.3 – Thermal Camera Gobi-384 Industrial (Xenics) [119]. ... 53
Figure 4.4 – Thermal Camera Fluke Ti25 [120]. ... 53
Figure 5.1 - Main complaints in 2015 at Continental Mabor [121]. ... 58
Figure 5.2- Processed images the experimental group. ... 82
xii
List of Tables
Table 2.1- Different classifications adopted in different countries [4]. ... 8
Table 2.2 – WMSDs grouped by affected anatomical areas [2, 4]. ... 11
Table 2.3 - WMSDs grouped by type of pathology [2, 4]. ... 11
Table 2.4 - Risk factors for the occurrence of MSIs [3]. ... 14
Table 2.5 - Some studies that was used as thermography as a diagnostic tool [94-96]. ... 29
Table 2.6 - Some studies in which the thermography was used as an evaluation tool of exposure to risk factors for development of MSIs [98-101]... 30
Table 3.1 – Operations supported by function bwmorph [110]... 38
Table 3.2 – Edge detectors available in function edge [110]. ... 42
Table 3.3 – Regional descriptors computed by function regionprops [110]. ... 46
Table 4.1 – Characteristics of thermal camera Gobi-384 Industrial (Xenics) [117]. ... 53
Table 4.2 – Characteristics of thermal camera Fluke Ti25 [118]. ... 54
Table 4.3 - Characteristics of the 52 tested images. ... 55
Table 5.1 – Patient Diagnosis. ... 58
Table 5.2 – Imagens unprocessed with injury and uninjured. ... 64
Table 5.3 Results of Diagnosis. ... 84
xiv
Abbreviations, Acronyms and Symbols
List of abbreviations and acronymsCTD Cumulative Trauma Disorder CTS Carpal Tunnel Syndrome DGS Directorate General of Health
ESWC European Survey on working Conditions EU European Union
EU-OSHA European Agency for Safety and Health at work EWA Ergonomic Workplace Analysis
FDI First Dorsal Interosseous FPA Focal Plane Arrays
HRM Highly Repetitive Movements
IACT International Academy of Clinical Thermology IEA International Ergonomics Association
IPT Image Processing Toolbox IR Infrared
IRT Infrared Thermography
LART Lesion Atribuable aus Trauvaux Répétitifes LCT Liquid Crystal Thermography
LoG Laplacian of a Gaussian LW Long-Wave
MDT Mean Dorsal Skin Temperature MSIs Musculoskeletal Injuries
MW Midwave
MWT Microwave Thermography OA Osteoarthritis
OOS Occupational Overuse Syndrome QNM Nordic Questionnaire Musculoskeletal RBV Relative Blood Volume
RSI Repetitive Strain Injuries SW Shortwave
TMS Troubles Musculosquelettiques Tsk Skin Temperature
UEMSD Upper Extremity Musculoskeletal Disorder UL Upper Limbs
xv USA United States of America
VPT Vibration Provocation Test
WMSDs Work-Related Musculoskeletal Disorders
List of symbols
ε Emissivity
σ Stephan-Boltzmann constant T Cutaneous Absolute Temperature K Boltzmann Constant
h Planck Constant c Speed of Light B Spectral Radiance
W Radiant Energy Flux Emitted f Imput image
g Image logic
1
Chapter 1
1.
Introduction
1.1 - Problem Description
Currently, skeletal muscle injuries are a major public health problem that affect millions of workers all over the world. These lesions are of great concern because they affect workers health and increase business and social costs. In the present study we give attention to musculoskeletal injuries (MSIs), studding them in enterprise environment because theses is the ambience where workers are constantly subjected to very demanding efforts, hence, resulting, very often, in pathologies such as lumbago, shoulder pain, neck pain, knee pain and many others. Diagnosing these diseases is not always an easy task, and even harder is to identify the exact point of the lesion without the help of technological equipment. In order to help health professionals to overcome these difficulties is, many times, used Infrared thermography (IRT), a technology that helps minimize absenteeism and increase the success rates of lesion treatments.
1.2 - Framework
Muscle injuries are very common in athletes, labourers, individuals that perform repetitive movements or in physically active persons, and they are characterized as a type of MSIs. These lesions have to be treated, and the treatment depends on the diagnosis and monitoring the state of the lesion.
Muscle damage is now very common and usually happens because the muscle was stretched beyond its limits, or because he was forced to borrow heavily. These lesion arises due, for example, to muscle overload and occur at high speed and load muscles and tendons, leg (quadriceps), spine and biceps [1].
The WMSDs acquired a lot of notoriety all over the world because it affects millions of workers in different sectors of activity. In the United States (US) about 60 million operators have symptoms of this type of injury, and in Europe it is considered one of the 10 most prevalent diseases of occupational origin [2].
These lesions require great attention because, as already mentioned, in addition to affecting the worker health it also affect the company, reducing productivity and increasing
absenteeism [3]. It is important to note that millions of European workers affected by MSIs, costs billions of euros in lost of productivity and social costs [4].
These workers are from various sectors, but one that has greater risk is the industry sector because it is a professional area that demands de moving of loads, such as vehicles, furniture and textiles [2].
Of all Member States of the European Union (EU), Greece is the only country that overcomes Portugal in regards to the eminence of workers with spine pain and UL. The MSIs of the spine and the UL, currently have a very significant importance [5]. In 1998, the most industrialized districts of Portugal were Lisbon, Porto and Setubal, and, in these regions, MSIs occupied the first place in the occupational diseases [6].
Thermography may have an important role and a great clinical application in the assessment of individual muscle injuries, which are difficult to diagnose. These technique can offer two types of important information when it comes to evaluate a muscle injury: it can locate an area of inflammation associated with a muscle or muscle group and it can illustrate atrophy well before it becomes apparent clinically [7].
IRT is a simple, non-invasive and inexpensive technique that provides valuable information to determine whether to continue with more specific studies [8,9]. This technique does not use radiation of any kind, so it can be used in children and pregnant women without any risk. In addition, it can be repeated as often as necessary, with assurances regarding the repeatability of results.
The IRT differs from usual radiographic studies of image that show structural abnormalities because it t allows the expression of physical and functional changes that justify the patient's symptoms. The type of thermal change depends on the intensity of the biological phenomenon that is occurring, and the size and depth of the tissue involved [8].
Originally, thermography was developed for military purposes but, currently, it is widely used for engineering applications and, in the last 50 years it’s also used for medical imaging [10].
IRT has also been used as an adjunctive assessment method in several cases, such as WMSDs [11], muscle damage induced by exercise [12], ulcer prevention study by pressure, prevention, detection and tracking of injury gymnasts [13].
It is believed that in recent years the presence of injuries in the workers muscles has increased, due to limited information on the topic. Therefore, this study aims to contribute to the knowledge of the actual scale of the problem, and the data prevalence beyond muscle injuries in workers caused by physically demanding jobs in industrial operations.
The image of use in medicine is currently considered an important resource in the development of medical diagnostics. The processing and image analysis focuses on developing procedures for extracting information of an image appropriately for their computer processing [14].
According to health authorities representing that represent company’s, there are several operators with symptoms of muscle injuries, mainly in the arms and spine, but it is unknown to what extent is the severity of an injury. These injuries occur because the workers are constantly subjected to repetitive movements, the movement of heavy loads and awkward postures while working. Thus, we intend to proceed with the use of thermography as a preliminary diagnostic tool in detecting and monitoring this type of lesions. For that it becomes necessary to initiate an improvement of the thermal images with MSIs in order to facilitate observation of medical and other technical detection.
Goals 3
1.3 - Goals
According to the topic of the present thesis “The use of thermal infra-red imaging to reveal muscle injuries caused by physically demanding jobs in industrial operations” the objective of the project is to evaluate the possibility of using thermography as a preliminary diagnostic tool in detecting and monitoring trauma and injury occurrences. It’s also our aim to sustain that is a simple, compact and cost-effective technique, that is suitable for a clinical environment and many advantages such as being reliable and of straightforward interpretation, allowing real-time monitoring during the diagnosis.
It is expected that tasks such as hardware selection, setup, image processing, clinical trials are accomplished along this project.
1.4 - Work Organization
In the following chapter, State of the Art, the prominent issue is the MSIs. In this chapter we are going to make a theoretical review of the subject and also a general review to consider these injuries in a worldwide perspective. After this first approach it will be presented the thermography as the solution to the problem. Deepening the theme of thermography we also are going to present their types, giving more emphasis to IRT because it is used in this work. At the end of the chapter, is made the description the use of thermography in two different ways and presented some applications of IRT, as in WMSDs, muscle injuries and physical exercise.
The third chapter is fully devoted to image processing and analysis, covering the algorithms used in this project.
In the fourth chapter presents the methodological procedure, which is displayed throughout the procedure performed in this work.
The main results obtained and discussion in the practical component are presented in the fifth chapter.
5
Chapter 2
2.
State of the Art
In the present chapter the prominent issue is the MSIs. In order to fully analyse it we present a theoretical review about the theme also considering an Ergonomics and Ergonomic Workplace Analysis, in the beginning of the chapter, as a way to fulfil the need of broad understanding of the main theme.
The MSIs and WMSDs is presented in section 2.2 and at 2.3 we are going to grapple Thermography presenting it as the solution to the problem. Still in this chapter we address to Thermography considering the concept of Liquid crystal thermography (LCT), Microwave thermography (MWT) and IRT. Section 2.5 is about Thermography and WMSDs and highlight the connection between the two main concepts. In the end of the chapter, section 2.6, conclusions are made.
Ergonomics
The word ergonomics comes from the Greek, ergo, meaning work, and nomos, as the Greek word for laws or rules. Considering its etiology we can synthesize ergonomics as the laws governing work [15]. Nowadays there are various definitions for ergonomics, but some of them can lead us to a wrong interpretation because, sometimes it also refers to the "human factors engineering" or simply "human factors" [16,17]. In August 2000, the International Ergonomics Association (IEA) presented the official definition of ergonomics, describing it as "scientific discipline related to the understanding of interactions among humans and other elements or systems, and the application of theories, principles, data and methods, projects to optimize human well-being and overall system performance” [16].
The Ergonomics is defined by many authors as a set of scientific knowledge relating to man and necessary for the design of tools, machines, device and environment that can be used with the maximum comfort, safety and efficiency in their jobs. As a science it involves the application of knowledge of anatomy, physiology, psychology, biomechanics and anthropometry and can be stated as the solutions arisen from this relationship, it is concerned primarily with the physiological aspects of project work and with the human body and how it should adjust to the environment [17, 18]. In this sense, ergonomics studies aspects such as posture and body movements (sitting, standing, pushing, pulling and lifting weights); environmental factors (noise, vibration, lighting, thermal environments, chemicals); information (captured by vision,
hearing and other senses) and tasks. The correct combination of these factors represented in the figure 2.1, contributed to the success of any ergonomics program, as it enables , healthy, comfortable, efficient and safe working environments.
Figure 2.1 - Factors contributing to the success of an ergonomics program [19].
The IEA divides ergonomics in three areas of expertise. Therefore we have Physical
Ergonomics consisting on characteristics of human anatomy, anthropometry, biomechanics and
physiology of physical activity. It includes material handling, physical arrangement of workstations, work demands and factors such as repetition, vibration, strength and static posture related MSIs.
It also
features
the Cognitive Ergonomics that is related to the mental processes such asperception, memory, reasoning and motor response that affect the interactions of humans and other elements of a system that includes mental load, monitoring, decision making, performance skills, human error, human-computer interaction and training. And finally, it the area of Organizational Ergonomics with refers to the optimization of socio-technical systems including shift work, work schedule, job satisfaction, motivational theory, supervision, teamwork, teleworking and ethics [20].
Ergonomics can be applied in various sectors of activity. Everyday household is an example of that, such as industry, education, services and transportation. Currently, the word ergonomics is used to describe the science of designing a task that suits the worker, instead of forcing the worker to adapt to the task.
Ergonomic Workplace Analysis
One of the methods most used today is the EWA that consist in a realistic analysis of the work, in order to identify and evaluate the action of the main conditions that may affect the work, the worker and the organizational context.
Ergonomics 7
The EWA unfolds in three stages: first, the analysis of demand, secondly the analysis of the task and, finally, the analysis of the activities. The analysis of demand is the first phase of the EWA process, and aims to define with perspicuity the problem to be analysed doing so starting from a negotiation with the various actors involved (managers, supervisors, workers, ergonomists) [21]. The conditions of the work environment, such as environmental temperature, postural conditions for workers and the noise level, can be checked from this analysis. On the other hand, we have the ergonomic analysis of the task consisting in the analysis of work, technical and organizational environment. Finally, the ergonomic analysis of activity that corresponds to the analysis of the behaviour of human beings at work (gestural, informational, regulatory and cognitive). No worker should be exposed for more than 50 minutes without break to recovery, after that period of time. And it’s important that 10 minutes are devoted to recovery in order to avoid future health problems. WMSDs arise in individuals who are exposed to repetitive and continuous activities. These group of workers often presents complaints of pain, which mainly affect the UL. MSIs are already considered a major public health problem, and, in the workplace, is considered the most serious one, affecting workers all around the world. The change of function or worker's departure from his job can contribute to a healthy recovery when the worker accuses injuries of this type. The ergonomic intervention focused only on work organization is not the best option to solve the workers health problem [18].
A good job helps prevent fatigue and musculoskeletal disorders that may be followed by more generalized fatigue and postural distortions that results from bodily adjustments made to achieve better visualization of components placed inappropriately [17].
Musculoskeletal Injuries
The musculoskeletal system of the human body consists of several organs and tissues which function is to promote movement and locomotion. When there’s a malfunction MSIs can occur. The MSIs lead to inflammatory and degenerative diseases, and can be conceptualized as a disorder of the musculoskeletal tissues, such as muscles, joints, tendons, ligaments, nerves and bones. It also relates to localized diseases of the circulatory system. These injuries are often associated with temperature changes on the skin surface (inflammation, pathological or vasoconstriction vasodilation, paresis or plagiarise, atrophy, etc.) [22, 23].
The presence of a pathology may affect the thermal balance in place, increasing (e.g. inflammation contraction or muscle) or decreasing (e.g. reduced blood flow or decrease in muscle activity) Tsk. It also exists a condition where there is asymmetry of more than 0.7ºC [24].
The MSIs are recognized by the EU as one of the main causes of poor living quality and absenteeism. Currently physical factors in the workplace have been linked to this type of injury as well as leading to several consequences on the enterprise level, such as an increase in costs, a loss of productivity in the labour field and competitiveness [25, 26].
2.2.1- Work-Related Musculoskeletal Disorders
WMSDs has not always been a subject of attention or importance by the occupational health community in fact until the first half of the twentieth century little or nothing was known about this type of injury [5]. However, nowadays, it is considered the main factor behind injuries that cause disabilities, work absences and extreme care needs. The increase of company’s competitiveness, and the highlighting of productivity with lower costs, came to emphasize the problem and promote the development of studies in order to surpass it, so that the capitalized industries could obtain gains in the work pace and long shifts, bypassing ergonomically unsuitable environments [27, 28].
The WMSDs as mentioned above, affects the "work force" and represents one of the largest categories of occupational diseases. The relationship between MSIs and work is already formally recognized, and keeps as a mainstream subject to scientific community, because the relationship between the appearance of diseases and the ergonomic on the work place is not always very clear [23,26].
The lesions we have been taken in consideration are defined by the European Agency for Safety and Health at Work (EU-OSHA) as an organic structure of injuries such as muscles, joints, tendons, ligaments, nerves, bones and localized circulatory diseases caused or especially aggravated by occupation, and by the effects of the immediate environment where this activity takes place [3].
According to the General Health Department of Portugal, the WMSDs can be described as injuries that result from the action of professionals risk factors which occurs repeatability, and also results from a bad posture adopted during work, having also to be considered factors as duration, frequency and intensity (magnitude). Repeatability, as a matter of fact, is a major factor in de increasing of WMSDs rates. This factor relates to the fact of an individual being performing repeatability identical movements for over two to four times per minute, over 50% of the work cycle time for a total of 8h, which corresponds to one working day, in our country.
The symptoms of WMSDs may be pain, numbness, feeling of heaviness, fatigue and feeling of loss of strength. These symptoms are most evident on the worker at the end of a working day or even in production peaks.
The problem with this type of injury is that, at an early stage, symptoms are not perceivable. Instead, when the development is detected, because injuries are already installed, there are not much to do in order to avoid the problem. Injuries are there and, more often, affect the spinal column, also, the knee and the ankle [29]. After a literature review, it was concluded that there are several classifications to these lesions, depending on the country, as we can see in Table 2.1.
Table 2.1- Different classifications adopted in different countries [4]. Country Nomenclature
United States of America (USA) Comulative Trauma Disorders (CTD) United Kingdom Repetitive Strain Injury (RSI) or WMSD Sweden Occupational Cervicobrachial Disorder Brazil Lesões por Esforços Repetitivos (LER)
Distúrbios Osteomusculares Relacionados com o Trabalho (DORT)
Musculoskeletal Injuries 9
Australia Occupational Overuse Syndrome (OOS)
France Lésion Attribuable aus Trauvaux Répétitifes (LART)
Canada Repetitive Strain Injuries
Troubles Musculosquelettiques (TMS)
Portugal Lesões Músculo-esqueléticas Relacionadas com o Trabalho (LMERT)
2.2.2- Incidence of work-related musculoskeletal disorders at a
world level
The WMSDs acquired a very important patency in the world, affecting millions of workers from different sectors of activity. In the US, about 60 million operators
feature
symptoms of this type of injury, and in Europe these disease is considered one of the 10 most prevalent disorder with occupational origin [2]. Neurological diseases, lung diseases, diseases of the sensory organs, and skin diseases are some examples of other health disorders that have high prevalence rates in the EU (Figure 2.2).Figure 2.2 - Proportion of occupational diseases in Europe workers in 2005 [30].
These lesions require great attention, because as already mentioned, in addition to affecting the workers health they also affect the company, reducing productivity and increasing absenteeism [3]. Thus, it is important to note that millions of European workers affected by MSIs, costs Europe billions of euros in lost productivity and social costs [4], these workers are from various sectors, but the industry that represents the greater risk is the one that demands the move of loads, such as vehicles, furniture and textiles [2].
The US, Nordic countries and Japan are the countries that have a longer track record of occupational diseases worldwide, about one-third. Comparing the developed countries with the developing countries, it appears that WMSDs in developed countries account for about 3.4% of total global professional illnesses unlike developing countries that account for about 1.7%. It is assumed that one of the reasons for these figures is the fact that in developed countries there is a greater knowledge and greater awareness of workers and health professionals [6].Of all
members of the EU States, Greece overcomes Portugal, regarding the eminence of workers with spine pain and UL. The MSIs of the spine and the UL, currently, have a very significant importance [5]. In Portugal, the low spine pain has a share of 2.85% and 3.66% in the construction industry and lesions in the UL (shoulder and wrist) contain a percentage of 1.5%, 16.2% and 2:43% in the electrical industry, electronics and automotive [31]. In 1998, the most industrialized districts of Portugal were Lisbon, Porto and Setubal, where MSIs occupied the first place in the occupational diseases [6]. In the figure 2.3, we can see that the workers consider that work affects health in a meaningful way, being the spine pain and muscle pain the most significant health problem among these population [30].
Figure 2.3 - Percentage share of workers reporting health problems [30].
As mentioned earlier, the industrial workers are those with an increased risk of developing WMSDs due to the heavy and repetitive work. A study has shown that 92% of these
risk group is
suffering from this type of injury in any region of the body, being the lumbar region the one that is most prevalent, presenting an affected rate of 54%, then the neck, 43%, and, finally, shoulders with 42% [32]. Currently, there is still much research in this area to be made, either at national and international level, in order to try to better statistics.
2.2.3- Main Types of Work-Related Musculoskeletal Disorders
The WMSDs are associated with a group of pathologies of lower evolution and manifest themselves in terms of tendons, muscles, nerves, joints, and vascular system [27]. These lesions, that are associated with occupational activities, may occur due to a repetitive work, postural maintenance and/or manual inappropriate loads over a prolonged period of time. The main lesions affecting workers exposed to repetitive work, postural maintenance and/or handling charges are the neck pain, spine pain and injuries in the UL and lower limbs [3].The main WMSDs, shown in Tables 2.2 and 2.3, can be grouped by affected anatomical areas (such as shoulder / neck, spine, knee, elbow, hand and wrist) and type of pathology [29, 33].
% w
or
ker
Musculoskeletal Injuries 11
Table 2.2 – WMSDs grouped by affected anatomical areas [2, 4]. Anatomical Area Injuries
Shoulder and Neck
Syndrome conflict or thoracic outlet
Trapezius myalgia, Cervical syndrome, biceps tendinitis
Tendinitis of thorny above, Bursitis sub-acromion-deltoidea
Tendonitis of the rotator cuff
Elbow Radial tunnel syndrome, Cubital tunnel syndrome Elbow bursitis, epicondylitis and golfer's elbow
Hand and Wrist
Guyon's canal syndrome, Carpal tunnel syndrome (CTS)
De Quervain's disease, Köhler disease Tendinitis of the flexor / extensor wrist
Hand hygroma, Raynaud's syndrome, rhizarthrosis Digital stenosing tenosynovitis, Kienböck Disease Hand cramps, contracture of Dupuytren
Knee Bursitis prepatellar, gonarthrosis Spine Neck pain, spine pain, slipped discs
Table 2.3 - WMSDs grouped by type of pathology [2, 4]. Typology Injuries
Injuries at the level of the tendons Tendinitis, tenosynovitis, Stenosing tenosynovitis, synovitis, Peritendinites, ganglion cysts, Epicondylitis lateral or median, De Quervain's Disease Dupuytren's contracture
Lesions on peripheral nerves CTS, Guyon's canal syndrome,
Syndrome of the radial channel, Cubital tunnel syndrome, Pronator teres syndrome, Thoracic outlet syndrome, digital neuritis
Muscle injury Focal dystonia, fibromyositis, Myositis, myalgia, cervical muscle strain
Muscular and neuromuscular injuries Thrombosis of the ulnar artery syndrome of hand arm vibration syndrome hypothenar
Injuries in terms of articulating or synovial bags Injuries in terms of articulating or synovial bags
The major WMSDs are:
Carpal tunnel syndrome (CTS) - One of the most common neuropathies that constitutes a
peripheral nerve injury, caused by compression of the median nerve in the carpal tunnel lying on the pulse (Figure 2.4) [34]. This pathology is caused by repeated and vigorous movements of the hand and wrist as well as the use of vibrating tools [35] and is more common in middle-aged individuals and women. The first symptoms that differentiate the syndrome are intermittent numbness or tingling and burning sensation in the fingers [36].Patients with this disease in progression tend to have more symptoms, including progressive weakness, difficulty, suffering, palm or hand dry bright and lack of positioning of the upper limb [37]. It was carried
out a study among industrial workers that stated a prevalence of CTS 9,4 cases per 100 employees [38].
Figure 2.4 - Pressured at carpal ligament [34].
Tendonitis - Tendonitis is an inflammation of the joint area between the muscle and the
tendon [2] and may occur in the hand, wrist, elbow or shoulder. When there is excessive carrying out work, such as repetitive flexion/extension of the wrist and fingers, the tendon tends to be excessively exerted, and that will cause swelling due to inflammation [29].Later tendinitis generates a local sensitivity in the flashpoint and when joint movements are affected it generates a sharp pain [36].
Tendonitis of the rotator cuff - Is the most common of shoulder disorders [38]. It appears
as a result of the practice of activities that require high sustained or repeated UL at shoulder level or above it, circumduction movements with the arms high and static contraction of the muscles of the shoulders will also trigger this disease [29].
Epicondylitis – This disease is characterized as an elbow tendinitis that causes intermittent
pain [39]. The epicondylitis can be side (if the pain is at the point of insertion of the wrist extensors), or median (if the pain is in the wrist flexors), and appears in response to the overload of the elbow or/and repetitive gestures and as a manifestation of poorly distributed excessive loads [40, 41].
In a study
accomplished
among industrial workers, it was found a prevalence rate of epicondylitis (average and lateral) of 5 cases per 100 [38].The lateral epicondylitis is an injury that occurs more frequently than the average and is the result of follows execution moves to tighten or hold with full flexion of the fingers repetitive sequence. The median epicondylitis may arise in the event of pronation of the wrist, the palmar flexion of fingers and wrists and palmar flexion with ulnar or radial tilt of the hand.Rachialgia- According to the Direção Geral de Saúde (DGS), the Portuguese government
institution for public health, the rachialgias are characterized by a severe pain in the spine that appears in consequence of an osteo-articular and/or muscle damage. This is one of the diseases that more often is associated with work, and its symptoms can vary because they depend on the affected area of the spine: cervical, lumbar or dorsal. The cervical and lumbar regions are more affected because they are the most mobile [29].
The more relevant MSIs among Workers in the industrial sector in Portugal, are the rachialgias with prevalence values for low spine pain of 2.3%, and for neck and spine pain 1.1% 0.8% [31].
Musculoskeletal Injuries 13
Muscle Injury-The skeletal muscle, one of the most abundant tissues in the human body, is
constantly exposed to various types of injuries [42]. Muscles are able to provide body balance, strength, flexibility and proprioception [43], they are specialized tissues formed by tiny protein structures (myosin actin), that grows in order to become larger and larger structures, microfibers, fibres, fasciculus and muscle group [44].
Muscle damage is very common, and usually happens because the muscle was stretched beyond its limits. (Figure 2.5). These lesions occur at high speed in load muscles and tendons, leg (quadriceps) and spine (the spine injuries are termed e.g. by rachialgias as mentioned previously) and biceps [1].
Figure 2.5 – Muscle Injury [45].
2.2.4- Risk Factors
A work that can cause the opposite effect on muscle is a risk factor (negative) [29] and increase the likelihood of developing a disease or injury [46].
There are several factors that contribute to the development of MSIs. Some examples are the manual handling of loads, repetitive movements, static or awkward postures, vibration, insufficient breaks, low temperatures, organizational factors, high demands and low job control [33]. According to a study by the European Survey on Working Conditions (ESWC) the stance of maintaining standing or in uncomfortable positions, repetitive work or with display screen equipment, and manual handling of loads, Figure 2.6, are strong reasons for the appearance of the disease [30].
Figure 2.6 - Risk factors for MSIs [30].
These factors can be divided into 3 groups (Table 2.4): risk factors related to physical activity – These are risk factors emanating from the realization processes of work activity [4, 30]; risk factors organizational and psychosocial -These are risk factors related to work but without biomechanical nature. These factor is connected with the subjective perception that employees have on aspects related to the organization of work [3]. The third group is related to individual factors, constituting a subgroup not work-related that includes personal characteristics [46].
Table 2.4 - Risk factors for the occurrence of MSIs [3]. Classification Risk factors
Related factors with the work activity or Physical
Force application, such as lifting, carrying, pulling, pushing or using tools.
Repetitive movements
Forced postures or static, for example, hands above the level of the shoulders or sitting or standing for a long period of time.
Located compression exerted by tools and surfaces.
Vibes
Cold or Excessive Heat Lighting
High noise levels
Psychosocial and Organizational Factors
Demanding work
Lack of support from colleagues, supervisors and managers
Low levels of job satisfaction
% wor ke rs ex po sed (1 /4 of the wo rki ng
Thermography 15
Monotonous, repetitive and with a fast paced work. Individual factors Age Obesity Smoking Physical Ability
Thermography
Thermography is a non-invasive technology that measures the variations in Tsk across the surface of the body through infrared (IR) and thermal imaging [47], a technology that stands in the principle that an object with a temperature above absolute zero emits IR radiation or thermal radiation.
The IR image or thermography is a method that captures and measures radiation emitted by the body, thus allowing an image of the thermal distribution on the skin surface. This radiation is detected by an IR camera, and the emitted radiation intensity is converted to a temperature measurement. From the thermographic inspection, the observed temperature distribution differentials, provides information related to a process that is occurring inside the organism.
According to the International Academy of Clinical Thermology (IACT), thermography is a comfortable and safe procedure [48].It is a promptly, painless exam, that doesn’t involve radiation or contrast substances [49].
The thermographic technique lends itself to countless applications in biology, thanks to its versatility, lack of invasiveness and high sensitivity. It is widely used in medical, chiropractic and veterinary areas [47, 50]. An example of its application is the assessment of the vascularization of solid organs and pathologies in soft tissues, thus establishing, a diagnostic aid component. It can identify thermal and vascular abnormalities, and is very suitable for studies relating to pain, which can be measured following therapeutic procedures for immediate review or long-term treatments [48].
The ease of use of the high thermal resolution (few centimes of Celsius degree depending on detector used), together with the fact of being non-invasive in terms os opportunities of use, have made thermography a technique widely used as a diagnostic tool [50]. Clinically, thermography can be used as a diagnostic tool, as an enhancer of the physical examination (because the camera is at least 10 times more sensitive than the clinician’s hand), or as a method to detect inflammatory situations [51].
Despite all the mentioned advantages this is an unfit technique to provide information about the ethology of diseases and cannot give any anatomical details on deeper organs and structures because of the general difficulty of heat diffusion through the fatty tissue and bones. However, it provides information on the location of pathological changes and physiological temperature.
Thermography is particularly useful on diseases that lead to alterations of the normal control of the body temperature, such as changes in the microcirculation, inflammation, trauma, metabolism and efficiency of the thermoregulatory systems [48]. It can identify and locate the anatomical region affected by lesions by pointing out a temperature difference of 1 ºC (Figure 2.7) [52, 53].
Figure 2.7 - Body temperature in: a) a cold environment; b) in the warm [54].
Thermography has been applied in some studies, as cancer diagnosis, muscle damage diagnosis, diagnosis of ischemia, in diabetic patients and evaluation of muscle recovery [55].
Clinical thermography has been in use since the 1960s and detects temperature variation on the surface of the skin. In the case of in breast cancer, thermography involves using a thermal imaging device to detect and record the heat pattern of the breast surface. Thermography does not provide information on the morphological characteristics of the breast, rather it provides functional information on thermal and vascular conditions of the tissue. The role of thermography is considered to be a complement to other techniques, as it is a test of physiology, this alone is not sufficient for medical practitioners to make or confirm a diagnosis [56].
This technique may not always provide specific pathology detail.
However, it assists in defining the localization of increased inflammation and/or injury area. The inflammatory response is characterized by the increase of the permeability of the blood vessels which results in the raise of the blood flow that alters the heat pattern. Therefore, variation in superficial thermal patterns resulting from changes in blood flow will alter the amount of radiated heat that may be identified without difficulty by thermography and may relate to inflammation of tissues underlying the appearance of changes in the metabolic activity [57].
As already mentioned before, this is a method used to record patterns of thermal gradients in the body and can be used to measure the thermal radiation (heat) emitted by the body. Considering this characteristics it may, therefore, be used in the process of diagnosing lesions caused by physical exercise. The thermography has been used, among other things, for example, to determine injuries of the musculoskeletal system [58].
It can be repeated as often as necessary because there is no risk or pain to the patient. The skin contains a thermal symmetry indicative of normalcy (Figure 2.8), when it is detected an asymmetric it means that there is a change in the organism. An increase in temperature indicates an increase of blood circulation, which is usually a process associated to pain, inflammation or other causes [59]. Figure 2.8 represents an example of a symmetrical temperature distribution of the knees from a healthy subject. In Figure 2.8a is represented the
Thermography 17
anterior view, where the patella appears as a cold shield due to bony structure. The muscles of the upper and lower leg represent hot areas due to high metabolic activity in the muscles. The posterior aspect of the knee (Figure 2.8b) shows high temperature in the popliteal fossa because of the popliteal arteries and veins [60].
Figure 2.8 - IR image of healthy knee: a) anterior aspect; b) posterior aspect [60].
Thermography is a process in which temperature differences can be mapped in a two-dimensional image. The process detects electromagnetic radiation emitted by a body or liquids that are at a higher temperature and takes advantage of Stefan-Boltzmann’s law, which states that the thermal radiation emitted by a body is proportional to the difference between the fourth power of the body and the fourth power of its surroundings [59].
W=
ε
σT4 , (2.1) where W is the radiant energy flux emitted by a surface area W / cm2, ε emissivity, 0,978, σ Stephan-Boltzmann constant, 5,673x10-12 W/Kx cm-2, and T cutaneous absolute temperature, K (Kelvin) [61].This makes thermography a powerful tool to detect even the smallest differences in temperature.
There are three types of thermography: LCT; IRT and MWT, which will be discussed in detail later. While LCT on takes advantage of the fact that certain organic compounds are optically anisotropic in the liquid phase and a colour change is associated with a change in temperature, IRT and MWT, on the other hand, allow observation and detection of light emitted from warm objects in the IR and microwave regions of the electromagnetic spectrum [59].
The main advantage of using thermography is that non-invasive and accurate measurements on many subjects can be taken in rapid succession [57]. However, thermography has more very significant advantages, as the absence of ionizing radiation, the safety and the low cost. The patient has no pain, there is no physical contact, the ability to provide temperatures of a real-time image surface, non-intrusiveness, possibility of locating the lesion, ability to demonstrate metabolic and physiological changes in a functional examination and lastly, it can be used a portable device [62].
Popliteal Fossa Patella
Types of Thermography
Thermography is a non-invasive technique in which temperatures are monitored, recorded and displayed in a two-dimensional image, allowing visualization of both thermal equilibrium and transient heating patterns. LCT and IRT are used to map surface temperatures, whereas MWT can map subcutaneous temperatures [61]. IRT and MWT, on the other hand, allow observation and detection of light emitted from warm objects in the IR and microwave regions of the electromagnetic spectrum, respectively. This makes IRT most suitable to record the temperature differences in clinical practice [59].
2.4.1- Liquid Crystal Thermography
Liquid Crystal Thermography (LCT) is a type of thermography relatively recent and widely used for clinical evaluation because is inexpensive, semi quantitative, and represents a contact method using liquid crystals [63, 64].
This thermal imaging method is a method of contact, as shown above, that allows the measurement of temperatures on skin surface [64].
The term “liquid crystal” denotes a state of aggregation of molecules that is intermediate between the crystalline solid and the amorphous liquid. In this state, a substance is strongly anisotropic in some of its properties, yet, at the same time, it exhibits a certain degree of fluidity, comparable, in many cases, to that of an ordinary liquid. An essential requirement that substances must fulfil to achieve a mesomorphic state (state of matter intermediate between a solid and liquid) is that their molecules must be highly anisotropic in their geometrical shape, (i.e. rod or disk shapes) [65].
Liquid crystals are applied to the area of interest and after placement, the crystal changes its neutral colour at room temperature, in response to the temperature of the body surface with which they come into contact. The resulting colour display is then photographed using Polaroid photography, giving a hard copy of the snapshot. It is this photography that shapes the thermogram, which is then used for the diagnostic assessment [64].
The liquid crystals used for thermal imaging are organic compounds that reflect the visible light in a narrow range, temperature-dependent wavelengths. The LCT system is simple, portable, commercially available and inexpensive. Biomedical applications include breast cancer detection and imaging of spinal root compression syndromes [61].
2.4.2- Microwave Thermography
MWT is the detection of microwave radiation from the human body. This procedure measures the emission of natural radiation in the microwave region of the electromagnetic spectrum [66, 67]. It can be repeated as many times as desired, without detrimental effects. Initial clinical assessments of MWT have been performed in breast cancer detection [66].
The technique was first described in 1975, being, at that time, used in joint disease. Some studies in the area of joint disease show that is easy to use this technique, and that it does not require a temperature controlled environment [67].
Types of Thermography 19
Unlike IRT and LCT, MWT enables reception of signals arising from thermal subsurface tissue [61]. There are some important and fundamental differences between IRT and MWT. The first technique uses wavelengths of 10 cm while the MWT uses longer wavelengths, typically 1-20 cm.
The microwave radiation can penetrate human tissue, therefore the emission will provide information relating to conditions within the subcutaneous body. The IR radiation is incapable of such penetration and thus, refers to conditions primarily at the surface.
Regarding the emission intensity of microwave, it is linearly proportional to the temperature transmitter. A measure of the emission can be easily connected with the emitter temperature. In a less direct manner IR intensity measurements can also be related to temperature.
The spatial resolution is also different in the two techniques: for microwaves it is around 1 cm, whereas the IRT typically conceived spatial resolutions of the order of 1 mm [66].
MWT attempts to directly observe the thermal radiation due to internal sources of the body, minimizing skin tissue contribution. The technique is, therefore, much less dependent on the measurement environment, and, in practice, it has been found possible to do entirely satisfactory measurements in normal clinical environment without the need for special facilities.
Thermography systems consists of a radiation receiving antenna that may be placed in contact with the surface, and a microwave radiometer receiver with is used for measuring the power of the thermal signal. To provide useful information in medicine, the MWT equipment must have a temperature resolution of about 0.1 º C and a stability measurement order of some tenths of Celsius degree. The equipment is portable, easy to use and suitable for routine use in a wide variety of clinical applications. This equipment was used to demonstrate that the MWT (Figure 2.9) can, simply and safely, provide clinically valuable information about disease activity by measuring the internal body temperature patterns. Both the detector LCT and the microwave require contact with the skin, which can change the thermal conditions of its surface [68].
2.4.3- Infrared Thermography
IRT is a simple technique, also non-invasive and inexpensive, that provides valuable information to determine whether to continue with more specific studies. The IRT measures emitted IR radiation and displays the information as a pictorial representation, called thermogram, the surface temperature of an object [8, 9]. The spectral bands 3-5 µm and 8-12 µm are used for IRT, because this minimizes absorption in air (Figure 2.10) [61].
Figure 2.10 - Medical imaging techniques within the electromagnetic spectrum [60].
This technique does not use extra radiation of any kind, so it can be used in children and pregnant women without any risk. In addition, it can be repeated as often as necessary, with assurances in what regards to the repeatability of the results. This is a complementary technique that provides a more functional professional information regarding the disease or injuries suffered by patients.
IRT allows, with a simple gesture of taking a picture or video, the saving of energy when it comes to register the radiating of the human body. This technique was first used in the medical field in the 60s, but, due to a poor performance as a diagnostic tool, the lack of standardized protocols, and the appearance of more accurate diagnostic techniques it ceased to be used.
In order to describe the performance of this technique is important to state that IR radiation emitted by the bodies under temperature is captured and quantified by sensors that detect this type of radiation and convert it into electronic images that can be viewed, scanned and recorded.
A thermographic camera is a device that, without contact with the object detects IR energy and convert it into an electrical signal which is then processed in a thermal image on a monitor
Types of Thermography 21
for analysis of different temperatures (Figure 2.11). The image obtained in the IRT can be considered as a heat map of the studied area, revealing the pathophysiological conditions associated with different disorders. Its medical use is based on human thermal physiology and the pathophysiology of skin thermoregulation [69].
Figure 2.11 - The thermal detector in an IR camera converts photon energy from a target surface into a
thermal image that can be displayed on a computer monitor. Each colour hue on the thermal image corresponds to a certain temperature interval [69].
Two aspects may be assessed: qualitative and quantitative variations in physiological thermal patterns. Qualitative variations are thermal symmetry changes that characterize the physiological thermal pattern; quantitative variations requires the determination of the temperature of the studied area and the existence of a temperature exceed 0.2-0.3 ºC over the thermal area around the location under observation.
The IRT differs from radiographic studies because this last one is used to show structural abnormalities, while IRT allows for the physical expression of functional changes that justify the patient's symptoms. The type of thermal change depends on the intensity of the biological phenomenon that is occurring, also depending on the size and depth of the tissue involved [8]. As mentioned above, the IRT measures the emitted IR radiation and displays the information as a pictorial representation of the temperature on the surface of the object through the thermogram. Each pixel in the thermogram represents the measured temperature surface of an object. The information can be displayed in colour scale (Figure 2.12a), in colour scale of strong-contrast (Figure 2.12b) and or as grey tones (Figure 2.12c). The colour scale contains the hotter and cooler areas in which the warmer areas are exposed in white or red and colder areas are displayed in blue or black [70].
Figure 2.12 - Temperature scales of thermograms: a) colour scale; b) colour scale strong-contrast; c)
grey tones [70].
Sometimes there are changes in skin temperature. They occur in there is a registration of variations in the thermal pattern (colour) that reflect thermal gradients. Patient conditions may not always be analysed in depth by thermography, however, this system helps to set the location of the area of inflammation and / or injury [57].
The infectious or inflammatory response is characterized by increased permeability of blood vessels, resulting in increased blood flow, which leads to a localized increase of the surface of the affected areas that changes the heat pattern of the area [57, 71]. Therefore, variation in superficial thermal patterns, resulting from changes in blood flow, will alter the amount of radiated heat that may be easily identified by thermography and may relate to inflammation on the tissues underlying that point or alterations in the metabolic activity [57].
The advantage of using IRT technique, compared to alternative methods that requires a contact between the object and the sensor, lies in the fact that the Tsk is not influenced by the presence of any probes that could modify the temperature variation of the surface through conduction (through direct contact between objects, molecular transference of heat energy) or through radiation (heat generated from within the body is given-off to the surrounding atmosphere) (Figure 2.13) [72].
Figure 2.13 - Thermal Transfer Processes [73].
IRT was originally developed for military purposes, about 50 years ago, but is currently used, with widely expression, for engineering applications and as a medical imaging technique.
A thermal imager is used for IRT to measure the heat pattern of the object surface or human skin and to detect the IR radiation [10].
Thermography has some very important advantages. Such as being a non-contact process, and, therefore, a hygienic reliable procedure that presents no risk to the patient, it is also
c)
Types of Thermography 23
applicable in real-time and dynamically, thanks to the advanced image processing software that exists nowadays. Another advantage is the fact that this technique is able to track evolutionary processes and as a high portability profile [8, 10].
Several studies concerning IRT special characteristics state that we can get additional information about the skin's thermal aspect and about the complex thermoregulatory process, The IRT is very useful in sporting activity because it allows to detect the possible injury or dysfunction, measuring the temperature of the skin over the inflamed joints: lesions or dysfunctions often impossible to been shown by conventional methods. IRT can be a new, e.g. diagnostic tool for detecting knee pathology, because it shows physiological changes, rather than anatomical changes [10].
A review of the literature on this topic demonstrated that IRT can be very important, because it is a particularly useful assessment tool for physicians who manage MSIs (i.e., physical therapists, physiatrists, and doctors of chiropractic). IRT is also useful in the diagnosis of pediatric MSIs in order to reduce the use of X-rays emitting ionizing radiation as much as possible [71].
Bone fractures often trigger an inflammatory response, and as it was mentioned earlier, when there is this type of response that there is a significant increase in Tsk in the affected area. The IRT is a useful addition to the diagnostic tools available to the physician since it can detect localized temperature variations such as occur when there is a fracture [9].
IRT is not the only technique that can be used to measure the Tsk, there are also thermal contact sensors (such as thermistors and thermocouples) which are an equally promising technique. However, the thermal interaction between the sensor and the atmosphere can reduce the reliability of the measurement. In case of wireless sensors, they provide great mobility and it does not interfere with physical activity. These sensors provide a continuous record of temperature in situations of high-dynamic or below or between layers of clothing [74].
IRT has been successfully applied for many clinical purposes (Figure 2.14). It has become more popular in recent years in research about sports physiology due to its non-contact and non-invasive nature (Figure 2.15) [75, 76].
Figure 2.14 - IRT images showing examples of varicose and superficial veins [75].
Figure 2.15 - Comparison of the pre-training and 24h post-training thermal image. (1) Subject of the
control group, pre-training; (2) subject of the control group, 24h post-training; (3) subject of the experimental group, pre-training; and (4) subject of the experience.
To obtain a correct value of Tsk by quantifying the emitted radiation, the emissivity of the measured surface must be known. Scientific studies that determine the emissivity of the human skin, mostly agreed that the emissivity was 0.978 [10].
2.4.3.1 - Factors Influencing Infrared Thermography
When working with the IRT we have to take into account certain factors, that can influence the assessment or interpretation of thermal images.
These factors will be divided into three main groups (Figure 2.16): Environmental factors, individual factors and technical factors. Individual factors, in its turn, are divided into intrinsic factors and extrinsic factors.
Environmental factors are those related to the location (natural features of the environment) in which the assessment is held. Some examples of these factors are: compartment size and room temperature, which is very important for most IRT applications. After a review of the literature, it was found that the ideal temperature stands between 18 º C to 25 º C and if the temperature is lower the patient may begin to tremble and becoming sweaty ever since the opposite occurs, that is, the temperature becomes high.
The ideal temperature is 21 º C since it is the temperature to which the skin IR emission values are higher; with relative humidity; correct atmospheric pressure. In this case, is given more emphasis to the temperature, because it is easier to control factor.
Individual factors are those that are related to the subject being evaluated and the personal characteristics that could influence Tsk. They are the most controllable and are divided into intrinsic factors - related to the biological and anatomical parameters, and extrinsic factors - those that affect the temperature of the human skin for a certain period of time. Intrinsic factors are: gender, age, anthropometry, height, weight, heart rate, hair density, emissivity of the skin, medical history, metabolic rate, skin blood flow, genetics and emotions. Extrinsic factors, are considered to be the admission factors affecting the Tsk or emissivity due to consumption or intake of medicinal products, beverages or other products that could temporarily influence the temperature of the skin, and also the application factors which are
Types of Thermography 25
the products applied directly to the skin that affect the flow of blood or emissivity of the skin, including cosmetics, ointments and radiation.
The last group of factors, the technical ones, are connected to the equipment used during the evaluation of IRT. The validity, reliability, protocol, camera characteristics, and statistical analysis programs are examples of such factors.
We can see that there are a large number of factors affecting the Tsk in humans, and is very complicated to control all them, but the fact that we have knowledge about these factors can help to prevent their influence or, at least, help in the recognition of their importance, thus ensuring the correct use of IRT [75].
Figure 2.16 - Representation of the classification of IRT-related factors in humans [75].
2.4.3.2
- Infrared Radiation
IR Radiation were discovered in 1790 by M. Pitke and in the very beginning of the XIX century (1800) the English astronomer Sir William Herschel, reminisced it while trying to figure out which colours were responsible for heating the objects. This astronomer believed that there are two kinds of radiation, light and heat radiation, sustaining that below the visible, red found exists a very powerful invisible radiation of calorific levels, that became known as IR radiation [77].
IR radiation is the region of the electromagnetic spectrum between visible light and microwaves, containing radiation with wavelengths ranging from 0.75 to 10 mm [78].
